In a projection exposing apparatus (a stepper) to be used in a photolithographic process for manufacturing a semiconductor device, a liquid crystal display or the like, a shape measuring apparatus for measuring a thing to be processed such as a wafer or an apparatus requiring precision positioning such as a high precision processing machine, generation of heat from a linear motor as a driving source might adversely influence performance of the apparatus.
In more detail, a support member of an armature winding and a surrounding structure, and atmosphere are heated so that temperature is raised by the heat generated from the armature winding of the linear motor, and precision in the positioning of an XY stage to be driven by the linear motor is remarkably deteriorated. In order to prevent the temperature of the armature winding of the linear motor from being changed, a linear motor comprising a cooling mechanism for forcibly cooling an armature winding has been disclosed in JP-UM-A-6-041381 and JP-UM-A-6-70484 which have been filed by the present applicant, for example.
FIG. 7 is a general perspective view showing a linear motor according to an example of the conventional art, illustrating an example of a moving-magnet type linear motor in which a field side is set to be a moving member and an armature side is set to be a stator.
In FIG. 7, 12 denotes a moving member, 13 denotes a moving base, 14 denotes a yoke, 15 denotes a permanent magnet, 21 denotes a stator, 22 denotes a stator base, 24 denotes a header, 25 denotes a refrigerant supply port, 26 denotes a refrigerant discharge port and 27 denotes a can. The stator 21 is constituted by the stator base 22, the header 24, the can 27 and an armature winding (not shown). The header 24 provided on both ends of the can 27 has the refrigerant supply port 25 for supplying a refrigerant to one of the both ends of the can 27 and has the refrigerant discharge port 26 for discharging the refrigerant on the other end. Moreover, the moving member 12 is constituted by the moving member base 13, the yoke 14 and the permanent magnet 15. The moving member 12 is supported to maintain a constant clearance with respect to the stator 21 by means of a linear guide which is not shown, or the like.
Next, the stator 21 will be described in detail.
FIG. 8 is a front sectional view taken along an A-A line in FIG. 7.
In FIG. 8, 28 denotes a passage, 29 denotes an armature winding and 30 denotes a winding fixing frame.
The stator 21 is made to have wholly inverse T-shape and the can 27 is supported upward in the dent of the stator base 22. The winding fixing frame 30 is provided in a space formed by a header sealing the can 27, the can 27 and a header (not shown), and furthermore, the armature winding 29 is fixed in the longitudinal direction of the winding fixing frame 30. There is provided the passage 28 for causing a refrigerant to pass through the inside of the can 27. The can 27 is provided in a magnetic field. Therefore, a non-magnetic material, for example, stainless, resin or ceramics is used.
With such a structure, a predetermined current is applied to the armature winding 29 to act on a magnetic field created by the permanent magnet 15, thereby generating a thrust on the moving member 12. As shown in FIG. 7, the moving member 12 can be moved in the direction of progress shown in an arrow.
Then, the refrigerant is supplied from the refrigerant supply port 25 provided on the stator 21 and is injected from the refrigerant discharge port 26, and thus flows in the passage 28 formed by the armature winding 29 and the can 27, thereby recovering the heat, which is generated from the armature winding 29 due to a copper loss, so as to alleviate a temperature increase at the surface of a motor.
In the conventional art, a high heat absorbing efficiency is required for the refrigerant in order to cause the flow of the refrigerant to be constant, thereby enhancing the cooling capability of the armature winding 29. However, it is desirable that the refrigerant should be chemically inactive in order to maintain the insulating characteristic of the armature winding 29. However, the inactive refrigerant generally has a poor heat absorbing efficiency.
Moreover, it is also possible to enhance the cooling capability by increasing the flow of the refrigerant. However, since the can is deformed under the pressure of the refrigerant, the refrigerant has a poor heat absorbing efficiency in its inactive state, and restrictions made by apparatus itself, there is eventually a certain limitation.
The invention has been made to solve the problems and has an object to provide a linear motor armature and a linear motor which can prevent the deformation of a can and can greatly reduce a rise in the temperature of the linear motor by improving a refrigerant passage using a conventional inactive refrigerant, and has a high cooing capability.